Project Summary Pelvic organ prolapse is a debilitating condition characterized by the downward movement of the vaginal wall and/or the uterus through the vaginal opening. Other pelvic structures such as the bladder, bowel, and rectum can also descend behind the vagina and uterus resulting in a variety of genito-urinary and bowel symptoms that severely impact quality of life. Deficiencies in connective tissue and smooth muscle cells of the vagina have been associated with pelvic organ prolapse. Consequently, it is thought that the deficient vaginal wall may be a significant factor in the progression of pelvic organ prolapse. Normal and damaged tissues are generally replaced by continuous recruitment and differentiation from tissue- specific stem cell populations in the body. However, this process is compromised with aging, resulting in an increase in prevalence of degenerative conditions especially after injury. Vaginal birth trauma and age- dependent tissue changes are major contributors to pelvic organ prolapse. Surgical treatment is the main option with a 30% risk of reoperation. There is a clear need for preventive and new treatment strategies. In the past decade, stem cell-based therapies have become attractive options to improve biocompatibility and tissue integration. The most commonly studied stem cell type is the adult mesenchymal stem cell (MSC) because these can be harvested and expanded in culture from patient?s adipose tissue, bone marrow, and endometrial tissue. While preliminary results appear promising, clinical results are not robust. Given the tremendous advances in stem cell technologies, specifically the ability to introduce a set of genes to derive pluripotent stem cells from somatic cells (a.k.a. induced pluripotent stem cells or iPSCs), there is now significant effort underway in translating this cell type into clinical therapies for multiple diseases. iPSCs can be differentiated into somatic cells of all lineages with rejuvenated properties. A differentiation protocol has been optimized to produce a homogenous population of smooth muscle progenitor cells (pSMC) from patient iPSCs. The overarching hypothesis is that pSMC, derived from patient iPSCs, will exert dual effects in damaged pelvic tissues: 1. pSMC will induce extracellular matrix protein deposition by host connective tissue, and 2. engraftment of pSMC will improve contractile properties of a weakened vaginal wall. These effects will result in restoration of the defects in the vaginal wall affected by pelvic organ prolapse. In this R21 proposal, animal and cell studies to test these hypotheses are outlined.